build fix

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58912 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/evtloop.h

@@ -104,6 +104,7 @@ public:
     virtual bool Dispatch();
     virtual int DispatchTimeout(unsigned long timeout);
     virtual void WakeUp();
+    virtual bool YieldFor(long WXUNUSED(eventsToProcess)) { return true; }
 
     // MSW-specific function to process a single message
     virtual void ProcessMessage(WXMSG *msg);